Motorola Gtx2000 Lcs2000 68p02945c70 O Manual

5-4 Disassembly & Reassembly
Assemble the Radio
Assemble the Control Head1. Insert the LCD frame with LCD and Zebra connectors into its
place.
2. Place the keypad onto the board assembly, making sure the
keypad is ßush with the board.
3. Rotate the potentiometer counterclockwise. Rotate the volume
knob counterclockwise. This will allow you to insert the
potentiometer smoothly into its place in the volume knob.
4. Make sure the speaker including the gasket is well positioned.
5. Connect the printed...

Radio Tuning Procedure 6-1
6Radio Tuning Procedure6
Radio Tuning
Procedure
GeneralAn IBM PC (personal computer) and RSS (Radio Service Software) are required
to align the radio. Refer to the applicable RSS Manual for installation and setup
procedures for the software.
To perform the alignment procedures, the radio must be connected to the PC, RIB
(Radio Interface Box), and Test Set as shown in Figure 6-6.
Figure 6-6  Radio Alignment Test Setup
BNC
RIB
RIB POWER SUPPLYCOMPUTER INTERFACE CABLEDATA...

6-2 Radio Tuning ProcedureFigure 6-7  Service Menu Structure
All SERVICE screens read and program the radio codeplug directly; you do NOT
have to use the RSS GET/SAVE functions to program new tuning values.
The SERVICE screens use the concept of the ÒSoftpotÓ, an analog SOFTware
controlled POTentiometer used for adjusting all transceiver alignment controls.
Each SERVICE screen provides the capability to increase or decrease the ÔsoftpotÕ
value with the keyboard UP/DOWN arrow keys respectively. A...

Radio Tuning Procedure 6-3
Tuning Procedure
Starting the Tuning
Procedure1. From the SERVICE menu, press F6 to select BOARD REPLACEMENT.
2. Press F2 for LOGIC OR RF BOARD replacement.
Note:Perform the following procedures in the sequence indicated.
Reference Crystal Data1. Press F2 to select REFERENCE CRYSTAL DATA.
2. Press F8 for PROGRAM VALUE.
Tx Power1. Press F3 to select Tx POWER.
2. Press F6 to key the radio. The screen will indicate that the radio is
transmitting.
3. Adjust the transmit power value...

6-4 Radio Tuning Procedure
Transmit Deviation
Balance (Compensation)
& Deviation LimitCompensation alignment balances the modulation sensitivity of the VCO and
reference modulation (synthesizer low frequency port) lines. Compensation
algorithm is critical to the operation of signaling schemes that have very low
frequency components (e.g. DPL) and could result in distorted waveforms if
improperly adjusted.
1. Press F6 to select TX DEVIATION CALIBRATION. The screen will
indicate the transmit test...

Theory of Operation 7-1
7Theory of Operation7
This chapter provides theory of operation information for the radio. It starts with
a block diagram level functional description of the entire radio. This is followed
by a detailed functional description for each of the four major functions that make
up the radio.
Introduction
OverviewThis section provides a detailed theory of operation for the radio and its
components.
The main radio is a single board design, consisting of the transmitter, receiver, and...

7-2 Theory of OperationFigure 7-1 800-MHz Radio Functional Block Diagram
Receiver Detailed
Functional DescriptionThe receiver is composed of four sections: receiver front end, receiver IF, receiver
back end and the audio signal Þlter IC (ASFIC) that is part of the controller
section.
The radio signal from the antenna switch in the PA section enters the Þrst bandpass
Þlter (FL5203). The Þrst bandpass Þlter has three poles, a 860-MHz center
frequency, a 20-MHz wide passband and a 40-dB rejection for image...

Theory of Operation 7-3 Figure 7-2 Receiver Functional Block Diagram
After the ampliÞer, the signal enters a second bandpass Þlter (FL5204), which is
identical to FL5203. The bandpass Þlter is Þxed tuned from 851 to 870 MHz.
After the second bandpass Þlter, mixer U5211 down-converts the signal to the IF
frequency.
The mixer is a passive double-balance mixer that gets a local oscillator signal in
the range of 805.9 to 824.9 MHz from the synthesizer and works on 4-dBm power.
The IF frequency is   45.1 MHz....

7-4 Theory of Operation¥Second IF ampliÞers
¥FM Demodulator
¥Audio ampliÞer
In addition to BBR IC, the back end contains the following components:
¥Second LO resonator for 44.645 MHz (Y5211)
¥Crystal Þlters for 455 kHz (FL5201, FL5202)
¥Demodulator Þlter (C5224)
The IF signal routed to BBR IC is ampliÞed, converted to 455 kHz, Þltered,
limited and demodulated.
Demodulated audio comes out of BBR IC at pin 28 and is fed to the ASFIC, which
is part of the radio controller section.
In addition to the audio...

Theory of Operation 7-5 This network forms a low-pass Þlter to attenuate harmonic energy of the
transmitter to speciÞcations level.
A forward-power detector follows the harmonic Þlter. This forward-power
detector is a microstrip printed circuit, which couples a small amount of the
forward energy and sends it to diode CR6506 where it is rectiÞed. This rectiÞed
signal (VFORWARD) forms the forward voltage which the power control circuit
holds constant. Holding this voltage constant (which is proportional to...